daily, to 11 years: 200 mg twice daily, ≥12 years: 500 mg twice daily) Longer treatment courses may be needed in HIV-infected children and other immunocompromised hosts Standard and contact precautions should be used for the incontinent child Gram-negative Enterics: Vibrio, E coli, Campylobacter, Shigella Several gram-negative enteric pathogens are more common in developing nations than in industrialized countries These include Vibrio cholera, enterotoxigenic, enteropathic, enteroinvasive, and enteroaggregative E coli, and Campylobacter ( e-Table 94.22 ) Cholera is characterized by painless watery diarrhea, and persons most at risk are those with low gastric acidity It can be easily spread in congregate settings, and is a major cause of diarrhea in camps for displaced persons The character of diarrhea varies based on E coli type, and some types produce a Shiga-like toxin Campylobacter is also a cause of dysentery (bloody stools with fecal leukocytes) in the United States, but is more common internationally The most at-risk group for Shigella domestically is the child in daycare In addition to the acute symptoms (which are more severe in immunocompromised hosts), patients with Campylobacter can also have postinfectious sequelae with Guillain–Barré syndrome, including the Miller Fisher variant (ataxia out of proportion to sensory loss, areflexia, and ophthalmoplegia) All three pathogens can be cultured on routine stool culture media The mainstay of therapy is rehydration Adjunctive antibiotic treatment is recommended to decrease symptom duration, decrease fecal shedding, and decrease secondary transmission Standard and contact precautions are recommended Schistosomiasis Schistosomiasis is caused by mammalian blood trematodes (flukes) in the Schistosoma genus Freshwater snails transmit the infection through penetration of intact skin Schistosomiasis is endemic in more than 75 countries worldwide including in Africa, the Middle East, China, Southeast Asia, Brazil, Venezuela, and the Caribbean Adult worms can live as long as 30 years, causing disease decades after patients have left an endemic area The clinical manifestations of the most common syndromes caused by schistosomes are summarized in eTable 94.23 The severity of chronic illness is associated with worm burden Those with low to moderate burden may never develop significant illness, while those with significant worm burden may develop mucoid bloody diarrhea and